This application claims the priority of German application 198 36 191.7, filed in Germany on Aug. 4, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a flight control device for improving the longitudinal stability of an automatically controlled airplane. Especially preferred embodiments of the invention relate to combat planes in a delta wing configuration which are artificially stabilized by means of an automatic control system.
For the longitudinal control of automatically controlled airplanes, the control flaps or adjusting surfaces provided for this purpose, on the one hand, are used for controlling the airplane and, on the other hand, are used for stabilizing the airplane in flying ranges in which the airplane is at or beyond the stability limit. In known state of the art airplanes, the feedback signals of the automatic airplane control system have been switched with essentially the same amplification to the actuators of all control edge flaps and particularly to the actuators for trailing edge flaps responsible for the longitudinal control.
For example, because of changed load conditions, such as outside loads, or because of a changed demand on the maneuverability of the airplane, control concepts of future airplanes will be required to automatically control airplanes with a greater rearward gravity center position and thus with a lower stability. In the case of airplanes which were unstable from the beginning or become unstable only because of such shifts of the center of gravity, it will then be required to stabilize the occurring instability by means of the adjusting surfaces. This results in higher adjusting speeds and larger deflections of the adjusting surface, which, however, excites the airplane structure more and, as a result, higher structural couplings will occur. This causes an increase of the aeroservoelastic instabilities which are to be avoided.
Since there is also a tendency toward softer wing structures, structure filters must be provided in the autopilot in order to avoid that the wing structure is excited to an unacceptable degree. However, such structure filters impair the efficiency of the autopilot so that these may have the result that the demands on the automatic control of the airplane can be met only in a limited manner.
It is therefore an object of the invention to provide a flight control device for improving the longitudinal stability of an automatically controlled airplane which supplies improved possibilities for meeting the demands on the control and the stabilization of the airplane.
This object is achieved according to certain preferred embodiments of the invention by providing a light control device for the longitudinal control of an automatically controlled airplane having adjusting surfaces which, viewed from the longitudinal axis of the airplane, are on the outside and on the inside and are provided for the longitudinal control, wherein the inner adjusting surfaces experience an amplification which is by one half or more larger than that of the outer adjusting surfaces for the stabilization and control of the airplane in its longitudinal axis.
This object is also achieved according to certain preferred embodiments of the invention by providing a flight control device for the longitudinal control of an automatically controlled airplane having adjusting surfaces which, viewed from the longitudinal axis of the airplane, are on the outside and on the inside and are provided for the longitudinal control, wherein for the stabilization and control of the airplane in its longitudinal axis, a maximal velocity is provided for the outer adjusting surfaces which is at least by one fourth lower than that for the inner adjusting surfaces.
In certain preferred embodiments of the invention the above mentioned control features can be combined with the provision of controlled forwardly positioned slats.
The control systems according to the invention have the advantage that only by means of an increase of the superimposing of the amplification in the forward branch of the automatic flight control system and thus of the actuating signals to the actuators of the adjusting surfaces situated close to the fuselage, a higher degree of maneuverability can be achieved and a greater amount of instability can be stabilized. As a result, the phase delay which occurs in the automatic flight control system because of structure filters to be provided in the automatic flight control system, in the area of the control fraction of the wing flap movements, is at least limited or even reduced so that therefore the unfavorable effects of structure filters onto the low-frequency transmission action of the airplane, particularly the control fractions, can be considerably reduced.